1. Field of the Invention
The present invention relates to an organic electroluminescence (hereinafter, referred to as “EL”) device applied to a flat panel display, a projection display, and an illumination device, and to a multi-color display apparatus using the organic EL device.
2. Description of the Related Art
Organic EL devices using electroluminescence of an organic material have been actively researched and developed. Of the organic EL devices, a top emission type organic EL device (in which substrate, reflective electrode, organic layer, and transparent electrode are laminated in order to emit light in this lamination direction) capable of preventing aperture ratio loss caused by wirings and thin film transistors (TFTs) is becoming mainstream.
However, an organic EL material is sensitive to moisture, and hence a structure in which a protective layer is formed has been proposed to improve reliability. A protective layer which is located on an upper electrode and contains silicon, oxygen, or nitrogen is disclosed in Japanese Patent Application Laid-Open No. H07-161474. In order to improve light extraction efficiency in the top emission type organic EL device, a technology of defining a refractive index and thickness of an organic capping layer located on an upper electrode is disclosed in Japanese Patent Application Laid-Open No. 2006-156390.
However, when a thickness of the protective layer disclosed in Japanese Patent Application Laid-Open No. H07-161474 is to be set to enhance light having a desired wavelength, to thereby obtain an effect of improving the light extraction efficiency as described in Japanese Patent Application Laid-Open No. 2006-156390, sufficient protection performance may not be obtained because the protective layer is too thin.